In order to enrich the sugar content of fruit juices in the past, the fruit, e.g. grapes, has been subjected to a freezing process prior to crushing to extract the juice. This is usually accomplished in a batch-type refrigerator or freezer box unit employing both cryogenic and mechanical refrigeration. The process is labor intensive and usually requires processing times of between 12 and 24 hours per batch of fruit.
In Germany, the so-called Ice Wine process has recognized the importance of pressing a grape which has been cooled to a temperature of between 0.degree. C. and -15.degree. C. An improvement on the German Ice Wine process is disclosed in French Patent Application 8600115, filed Jan. 7, l986 and titled "Process for Obtaining Must". Applicants disclose freezing fruit such as grapes at a selected temperature between -6.degree. and -15.degree. C. and pressing them in the frozen state to obtain an enriched juice, particularly one that is enriched in sugar. The process of the prior art has been used, for example, to save grapes that have been left on the vine too long and because of prolonged rain have absorbed extra water. By freezing the grapes and crushing them, the water can be separated out as ice, thus having a must of more uniform sugar content.
Grapes from the same bunch have been shown to vary in composition. It is because of this compositional imbalance their freezing points and heats of solidification vary and are highly dependent upon the sugar content of the individual grape. Cold pressing of the grapes takes advantage of these thermodynamic properties by pressing the grapes at a temperature of between 0.degree. and -15.degree. C. Thus, the grapes can be pressed repeatedly at several warmer temperatures, to extract juices of decreasing quality. Employing this process has three distinct benefits. These are, an increased ability to extract musts due to cellular degradation at low temperatures, selective extraction by pressing at controlled temperatures, and concentration of musts by retention of ice crystals in the pulp during the processing. Unfortunately this process cannot be practiced on a commercial scale due to limitations in equipment and process technology.
Although no apparatus has been developed to effect the prior art process in relation to continuous processing of grapes for wine making, chilling of vegetables has been accomplished by devices such as shown in U.S. Pat. No. 4,697,508. However such a device would not be effective for handling fruit such as grapes because of the tendency to prematurely extract juice from the grapes.